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San Cayetano Mutual Water Co

What EPA’s and California’s records show in this utility’s water: nitrate, arsenic and other regulated chemicals; lead and copper; and violations since 2016, with the certification that handles each result.

Serves
109 people
Connections
69
Water source
Groundwater
Based in
Fillmore, CA
County
Ventura
Owner
Private
Hardness
Very hard
The 2 ZIP codes it serves

93015, 93060

The short answer

1 result is above the health goal. The worst: Uranium, above the health goal. No health-based violations on file since 2016.

What handles it

What was found

Uranium, nitrate, chromium (total), fluoride, arsenic and total trihalomethanes (TTHM): California’s own results, samples taken from March 27, 2020 to May 28, 2026, with EPA’s 2012 to 2019 file for earlier years.

Above the health goal1

Uranium

Comes from the source

Above the health goal

9.3ppb

Highest yearly average, 2023 to 2024

Averaged by year, the highest was 9.3 ppb, in 2024: below EPA’s legal limit of 30 ppb, but above its health goal of zero. That was also the latest year on file. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 9.1 ppb, in 2013.

What handles it

Below EPA’s limits3

Nitrate

Comes from the source

Below EPA’s limits

2.9ppm

Highest sample; found in 25 of 25

2026 average: 1.5 ppm

The highest sample, in 2025, was 2.9 ppm, below EPA’s legal limit of 10 ppm. In 2026, the latest year on file, its two samples averaged 1.5 ppm. Earlier, from 2012 to 2019, EPA’s file shows a highest sample of 9.0 ppm, in 2013.

What handles it

  • NSF/ANSI 58 look for “Nitrate/Nitrite Reduction”
  • NSF/ANSI 53 look for “Nitrate/Nitrite (30 ppm challenge)”

Chromium (total)

Comes from the source

Below EPA’s limits

27ppb

Highest yearly average, 2020 to 2026

Averaged by year, the highest was 27 ppb, in 2026, below EPA’s legal limit of 100 ppb. That was also the latest year on file. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 3.0 ppb, in 2013.

What handles it

Fluoride

Forms or is added in treatment

Below EPA’s limits

0.7ppm

Highest yearly average, 2020 to 2026

2026, one sample: 0.7 ppm

Averaged by year, the highest was 0.7 ppm, in 2020, below EPA’s legal limit of 4.0 ppm. In 2026, the latest year on file, its one sample was 0.7 ppm. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 0.8 ppm, in 2018.

What handles it

3 compounds tested and not foundBelow the reporting level in every sample. Not found is not the same as zero.
  • Arsenic
  • Lead
  • Total trihalomethanes (TTHM)

What handles it

A certification covers specific claims, not a whole standard. Look for these claims on the certifier’s listing, not the box. Wording varies a little: NSF writes “Lead Reduction,” WQA just “Lead.”

At the tap, or for the whole house?

These come with the water itself, so a whole-house system certified for the same claims treats every tap and shower. A filter at the tap treats drinking water for much less. How whole-house systems compare.

Filters with those claims on a certifier’s listing

None of the filters TapBuff has checked so far carry these claims. Search the certifier listings for the claim above.

Compare five-year costs

Hardness

Very hard, typically 526 mg/L (30.8 grains per gallon), across 4 sampling points, 2019 to 2026.

Hardness is calcium and magnesium. EPA sets no limit for it: it shows up as scale on fixtures and in water heaters, and as soap that won’t lather. USGS calls water above 60 mg/L moderately hard, above 120 hard and above 180 very hard.

Softeners compared at 30.8 grains per gallon, salt includedSoftener or salt-free conditioner?California water hardness, utility by utility

Violations since 2016

No health-based violations on file with EPA since 2016. There is 1 monitoring or reporting violation: a sample missed, late or not reported.

What this report can’t tell you

  • Everything else. Uranium, nitrate, chromium (total), fluoride, arsenic and total trihalomethanes (TTHM) results here are California’s own from 2020 on, with EPA’s national file for 2012 to 2019. San Cayetano Mutual Water Co’s own annual report, which it must send you every year, has the contaminants this page does not show.

  • Your own plumbing. Lead results are the 90th percentile across homes the utility samples. Your home’s service line, solder and fixtures decide yours. A certified lab test is the only way to know.

  • What it means for your health. This page reports what the records show and EPA’s limits and goals; it is not medical advice. If you are worried about a health effect, talk to a doctor or your local health department.

  • Anything after the latest data. SDWIS data is from 2026 Q3; UCMR 5 didn’t sample this utility; California’s results run from March 27, 2020 to May 28, 2026.

Testing your own tap

San Cayetano Mutual Water Co’s results are for the water it sends out. What your own service line, solder and fixtures add shows up only in a test of your tap, by a lab California certifies.

The 3 labs California certifies closest to the area San Cayetano Mutual Water Co serves, in a straight line. Call first: certification is test by test, and not every lab takes samples from homeowners.

  • Fruit Growers Laboratory, Inc.

    Santa Paula, CA · about 7 miles

    Certified for bacteria, nitrate, lead and copper, metals, minerals and other inorganics, organic chemicals, disinfection byproducts, radioactivity

    (805) 392-2000

  • Ventura County Public Health Laboratory

    Oxnard, CA · about 15 miles

    Certified for bacteria

    (805) 981-5131

  • Capco Analytical Services

    Ventura, CA · about 17 miles

    Certified for bacteria, nitrate, metals, minerals and other inorganics

    (805) 644-1095

All 145 certified labs for California

Sources

PWSID CA5601116. Rebuilt from EPA data on Oct. 18, 2026.

Towns it serves

Also in Ventura County

All California utilities

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